A Reverse Shock in GRB 181201A
A Reverse Shock in GRB 181201A
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DOI：
10.3847/1538-4357/ab40ce
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发表时间：
2019-07
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通讯作者：
T. Laskar;H. V. Eerten;P. Schady;C. Mundell;K. Alexander;R. Duran;E. Berger;J. Bolmer;R. Chornock;D. Coppejans;W. Fong;A. Gomboc;Nuria Jordana;S. Kobayashi;R. Margutti;K. Menten;R. Sari;R. Yamazaki;V. Lipunov;E. Gorbovskoy;V. Kornilov;N. Tyurina;D. Zimnukhov;R. Podesta;H. Levato;D. Buckley;A. Tlatov;R. Rebolo;M. Serra-Ricart
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作者：
T. Laskar;H. V. Eerten;P. Schady;C. Mundell;K. Alexander;R. Duran;E. Berger;J. Bolmer;R. Chornock;D. Coppejans;W. Fong;A. Gomboc;Nuria Jordana;S. Kobayashi;R. Margutti;K. Menten;R. Sari;R. Yamazaki;V. Lipunov;E. Gorbovskoy;V. Kornilov;N. Tyurina;D. Zimnukhov;R. Podesta;H. Levato;D. Buckley;A. Tlatov;R. Rebolo;M. Serra-Ricart
我们提出了全面的多波长无线电X射线观测的GRB 181201 A跨度从150秒到163天后的爆发，包括第一个联合ALMA-VLA-GMRT观测的伽玛射线暴（GRB）余辉。无线电和毫米波段的数据揭示了一个独特的签名，在103.9天，我们解释为反向冲击（RS）的排放。我们的观测首次提出了一个单一的射频频谱能量分布可以直接分解成RS和前向冲击（FS）组件。我们进行详细的建模的完整的多波长数据集，使用马尔可夫链蒙特卡罗抽样构建联合后验密度函数的基本物理参数描述的RS和FS同步辐射。我们发现并占所有发现的退化模型参数。联合RS-FS模型揭示了一个弱磁化（σ = 3 × 10−3）、温和相对论性的RS，由此我们推导出GRB喷流的初始体洛伦兹因子为Γ0 <$103。我们的研究结果支持了低密度环境有利于遥感辐射可观测性的假设。我们将我们的观测结果与其他具有强RS检测的事件进行比较，发现可能的观测偏差选择了更长时间的非相对论RS。我们提出并开始解决新一代的全面，多频数据集所带来的建模的新挑战。
We present comprehensive multiwavelength radio to X-ray observations of GRB 181201A spanning from ≈150 s to ≈163 days after the burst, comprising the first joint ALMA–VLA–GMRT observations of a gamma-ray burst (GRB) afterglow. The radio and millimeter-band data reveal a distinct signature at ≈3.9 days, which we interpret as reverse-shock (RS) emission. Our observations present the first time that a single radio-frequency spectral energy distribution can be decomposed directly into RS and forward shock (FS) components. We perform detailed modeling of the full multiwavelength data set, using Markov Chain Monte Carlo sampling to construct the joint posterior density function of the underlying physical parameters describing the RS and FS synchrotron emission. We uncover and account for all discovered degeneracies in the model parameters. The joint RS–FS modeling reveals a weakly magnetized (σ ≈ 3 × 10−3), mildly relativistic RS, from which we derive an initial bulk Lorentz factor of Γ0 ≈ 103 for the GRB jet. Our results support the hypothesis that low-density environments are conducive to the observability of RS emission. We compare our observations to other events with strong RS detections and find a likely observational bias selecting for longer lasting, nonrelativistic RSs. We present and begin to address new challenges in modeling posed by the present generation of comprehensive, multifrequency data sets.